Disabling Instant Messaging (IM) in Skype for Business 2015

This one that was difficult for me to find and google an answer for. All of the answers were for Lync or didn’t work. The organization I work for currently, has to be very careful what messaging tools our users have access to. Because of this, some extra measures have to be taken to disable or remove functionality that we aren’t able to log and store according to compliance & regulatory requirements. Something that has recently fell into that pot was instant messaging via Skype for Business (a little silly, I know). After hours of searching I found the following registry keys need to be put in place depending on the version of skype/office: